Discover these recent published findings about the toxicity of Formlabs Dental 3D resins even after printing and postprocessing: 

Fig. 2

As clearly highlighted in the mentioned scientific paper published by the Northwestern University (Chicago, USA), Formlabs’ Dental SG and LT Clear printed in Form 2 SLA 3D printer were toxic, despite being certified as biomedical devices. 

Similarly, the resin of Graphy for direct printing of aligners also resulted to be toxic as reported in this paper published in the European Journal of Orthodontics: Leaching from a 3D-printed aligner resin

Biocompatibility and safety failure can be due to an inadequate resin design from its conception, and/or due to an inadequate postcuring and postprocessing, leaving the aligner full of soluble leachables and extractables, unreacted monomers, residuals and reaction byproducts. 

Photopolymer 3D resins are liquid photo reactive raw materials, which photopolymerise or react with light in the printers, normally layer by layer, to cure or become printed solid materials with a specific shape. They need to be designed properly with safe non leachable / extractable ingredients after postcuring and postprocessing to ensure that they are fully cured and free of leachable / extractable contaminants, unreacted monomers, residuals and reaction byproducts.